How to create a trial version of a Java program [closed]

Answer 1

The problem with trying to limit the dates is that the naive solution of just checking the date is easily fooled if the person sets back their system clock. I worked with a guy who kept a VMWare virtual box just for running time limited software. A better approach would be to record the time of the last time it was run, and if the time ever goes before that time, you know the clock was set back and you can abort. The problem is figuring out how to stash that file somewhere where the user can't find it an overwrite it. Again, in the the VMWare or VirtualBox environment, the user could just roll back to an earlier snapshot.

In other words, you can limit some of the people some of the time, but not all of the people all of the time.

Answer 2

I've had success using True License in the past. It has a support for a trial period. Use it in combination with an obfuscation tool like ProGuard and it certainly makes it non-trivial to crack.

Answer 3

There's a product called Rampart that lets you make a trial version for your Java app. It only takes a couple of minutes and it works pretty well.

You can find it at http://Rampartlicensing.com

Answer 4

I would just do something really simple and just hard enough such that non-programmers wouldn't be able to figure it out.

I would something like write to a file the number of milliseconds when the program was first installed in a 64-bit long in binary to a file. And have your main class check and enforce the time limit. Yes people can change their clocks to work around this, but really you don't want to sell to those people anyways. Also ensure the current time is strictly within 30 days of the install. Most users will just set their clocks back one year and it works with most programs because they just did a simple less than the difference check. You should also check that the difference in number of days from current to install is also greater than 0.

If you feel you need more protection than that, then you have a business model problem more than a software one. Its basically impossible to make it unhackable, especially since you can just extract and disassemble the class files.

Answer 5

Why not just hard code an expiry date into the trial program so that you don't have to continue to support it? You could put this in main().

// Die after October 1, 2010
Calendar expireDate = Calendar.getInstance();
// January is 0 (y, m, d)
expireDate.set(2010, 9, 1);
// Get current date and compare
if (Calendar.getInstance().after(expireDate)) {
  // Die
  System.exit(0);
}

This is how Microsoft distributes their large scale beta software. They just give it an expiry date.

If you're talking about preventing reverse engineering or modifying the code, you can't. You could obfuscate the compiled program, but this won't stop the people who would be reverse engineering your code anyway.

Answer 6

I recommend functional limitions. I have little post it note program. The program works fully, but you can create only 10 notes in unregistered mode. So i try to be nice to user. No date limitions, nag screens or someting else evil. Only small status line that has limition text and and register button.